This application relates to fuses for use in, for example, electric circuits for automobiles.
Conventionally, fuses are used to protect electric circuits installed in automobiles, and in electric and electronic components connected to the electric circuits. More particularly, when overcurrent unexpectedly flows in an electric circuit, heat generated by the overcurrent blows the fusion portion of a fuse in order to block the overcurrent from flowing through to respective electric and electronic components.
There are various types of known fuses, one of which is a fuse 800 disclosed in JP Application No. 2013-020354, which is illustrated in FIG. 6A.
The fuse 800 disclosed in JP Application No. 2013-020354 has characteristics modified by welding a low-melting metal 823 to a part of a fusion portion 820 housed in an insulating housing 830 so that the low-melting metal 823 serves to, for example, better control temperature increases and improve durability.
However, since no change is made to the overall shape of the fuse 800 except that the low-melting metal 823 is welded to a part of the fusion portion 820 housed in the insulating housing 830, the fuse 800 is indistinguishable from the conventional fuses. The worst case scenario when a fuse with different fuse characteristics is mistakenly put in a fuse box would be that electric wires in the fuse box are burnt or broken.
Moreover, insertion of a fuse with different fuse characteristics in a fuse box for a high voltage circuit would involve the risk that overcurrent flows and blows the fusion portion of the inserted fuse, generating electric arc between sections of the blown fusion portion.
FIGS. 6B and 6C respectively illustrate a fuse 900A and a fuse 900B disclosed in JP Application No. 2000-058691 and JP Application No. 2000-099745 with an aim to prevent insertion of wrong products.
In these fuses, as illustrated in FIGS. 6B and 6C, their insulating housings in part, and housings of fuse boxes have modified shapes.
More specifically, because of its insulating housing 930A having a shape corresponding to that of the housing 950A, the fuse 900A of FIG. 63 can be directly inserted in the housing 950A. On the other hand, the fuse 900B of FIG. 6C is different from the fuse of FIG. 6B. Specifically, protrusions 931B are provided on both side surfaces of an insulating housing 930B, and a housing 950B has a modified, substantially rectangular shape corresponding to the shape of the insulating housing 930B.
An attempt to mistakenly insert the fuse 900B of FIG. 6C into the housing 950A of FIG. 6B would fail since the protrusions 931B on the side surfaces of the insulating housing 930B abut against the upper end of the housing 950A. In this way, it is prevented to mistakenly insert wrong products having different characteristics by modifying the shapes of their fuse housings and housings of fuse boxes.
FIG. 6D illustrates a fuse 1000 disclosed in JP Application No. 2001-273994, which has a blocking wall to block persisting electric arc.
When overcurrent flowing in the fuse 1000 blows a fusion portion 1020, electric arc may be generated between two root portions 1021 left with the blown fusion portion. However, a blocking wall 1031, which is formed in an insulating housing 1030 at a position between the two root portions 1021, can physically block persisting electric arc.
Although the fuses 900A, 900B, and 1000 disclosed in JP Application No. 2000-058691, JP Application No. 2000-099745, and JP Application No. 2001-273994 may prevent the insertion of wrong products or the occurrence of persisting electric arc, these structures are overly complex and expensive to manufacture.